When making a decision, the risk can be expressed as the
probability of wining vs. losing, or the outcome winnings vs. losses. We used a
novel gambling task with 30 subjects in fMRI to study the different roles of
fronto-striatal systems in the integration of probability vs. outcome. The
probability of winning correlated with activity in the rostral Ventral Striatum
(VS), dorsal anterior-cingulate (ACC) and orbitofrontal cortex. The magnitude
of winnings correlated with caudal-VS and subgenual-ACC activity. Conclusion:
separate regions of VS and ACC are sensitive to different aspects of risk, even
when the expected utility of choices is equated.